A significant number of auto accidents involve one vehicle colliding into the rear of another at relatively low velocities. The passengers in the rear car are subjected to the sudden deceleration resulting from a front end collision, and are protected by belts, bags, and compliant steering wheels. On the other hand, the impacted vehicle is accelerated forward, subjecting the passengers to impact forces to their backs and heads. In this collision mode, the seat back and headrest are supposed to restrain the passenger and absorb the impact energy.
An objective of the invention is to prevent relative horizontal motion between the passenger's upper body and head during the collision process.
A further objective is to absorb the energy of impact between the head and the headrest by means of entropic heat generation.